 Basil RathboneSherlock Holmes | Sherlock Holmes |
 Nigel BruceDoctor Watson | Doctor Watson |
| MMarjorie LordNancy Partridge | Nancy Partridge |
 Henry DaniellWilliam Easter | William Easter |
 George ZuccoHeinrich Hinckel aka Richard Stanley | Heinrich Hinckel aka Richard Stanley |
 John ArcherNaval Lt. Pete Merriam | Naval Lt. Pete Merriam |
 Gavin MuirMr. Lang, government agent | Mr. Lang, government agent |
 Edmund MacDonaldDetective Lt. Grogan | Detective Lt. Grogan |
 Don TerryHowe | Howe |
 Mary GordonMrs. Hudson | Mrs. Hudson |
 Bradley PageCady | Cady |
 Clarence MuseGeorge | George |
 Mary ForbesMrs. Pettibone | Mrs. Pettibone |
 Holmes HerbertMr. Ahrens | Mr. Ahrens |
 Thurston HallSen. Henry Babcock | Sen. Henry Babcock |
 Ian WolfeAntiques Store Sales Clerk | Antiques Store Sales Clerk |
| JJohn BurtonArmy Inspector (uncredited) | Army Inspector (uncredited) |
 Gerald HamerAlfred Pettibone | Alfred Pettibone |
 Gilbert EmerySir Henry Marchmont (uncredited) | Sir Henry Marchmont (uncredited) |
 Margaret SeddonMiss Pringle (uncredited) | Miss Pringle (uncredited) |
| MMary FieldParty Pianist (uncredited) | Party Pianist (uncredited) |
 Colin KennyHotel Doorman (uncredited) | Hotel Doorman (uncredited) |
 Caroline Frances CookeMrs. Ruxton | Mrs. Ruxton |
